<h2>Problem 152</h2>
<div style="color:#666;font-size:80%;">27 April 2007</div><br />
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<p>There are several ways to write the number 1/2 as a sum of inverse squares using <i>distinct</i> integers.</p>
<p>For instance, the numbers {2,3,4,5,7,12,15,20,28,35} can be used:</p>
<p style="margin-left:50px;"><img src="http://projecteuler.net/project/images/p_152_sum.gif" border="0" alt="" /></p>
<p>In fact, only using integers between 2 and 45 inclusive, there are exactly three ways to do it, the remaining two being: {2,3,4,6,7,9,10,20,28,35,36,45} and {2,3,4,6,7,9,12,15,28,30,35,36,45}.</p>
<p>How many ways are there to write the number 1/2 as a sum of inverse squares using distinct integers between 2 and 80 inclusive?</p>
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